Its many detractors have called it the "Frankenfish". They say it will leave poison on our dinner plates and spoil the marine environment.

Its proponents, meanwhile, argue that a genetically modified salmon could help preserve the oceans and feed the world for decades to come.

The GM Atlantic salmon grows twice as fast as its wild cousin. Its genes have been artificially augmented with DNA taken from two other fish – the Pacific Chinook salmon and an eel-like species called an ocean pout (Zoarces americanus) – in order to boost the growth hormone that allows it continually to put on weight throughout the year.

After two decades of research and development, and almost as many years of legislative wrangling, the company behind the GM salmon believes that it now stands on the verge of an historic decision by the powerful US Food and Drug Administration (FDA) that will open the way to the sale of genetically engineered meat and fish both in the United States and the rest of the world.

Yesterday, the FDA held a public consultation on the sort of labelling the GM salmon should be given, following an exhaustive scientific review which found there were few serious concerns about the risk either to human health or to the natural environment. A spokeswoman for the administration said a final decision on whether to approve the sale of the GM salmon eggs can now go ahead. "There is no timeline on a decision on the application, but I would predict it more along the lines of months, rather than weeks," she told The Independent.

The Massachusetts company AquaBounty Technologies believes it has done everything possible to show that farmed GM salmon will be both safe for humans to eat as well as being harmless to the marine environment – although this had done little to quell the concerns of its detractors.

There is little risk of the GM salmon escaping to the wild, because they are designed to be grown in fish-farm tanks on land rather than in pens out at sea. Even if they do escape, the fish will not interbreed with wild salmon because the GM eggs have been designed to develop into sterile females, said Ron Stotish, AquaBounty's chief executive.

But there is already fierce opposition to the principle of GM salmon from consumer groups, animal welfare organisations and environmentalists. A coalition of 31 such groups in the US has stated their implacable opposition to a product they believe is potentially dangerous to human health and the environment, as well as cruel and painful for the GM fish, which they say are created to grow unnaturally fast.

If the FDA gives its approval, which many commentators believe is now inevitable given that its scientists have found little to argue against doing so, the opponents of the GM salmon insist that it should at least be clearly labelled as a product of genetic engineering. "It is essential to label a genetically engineered animal so that any unexpected effects will be recognised and consumer health protected," said Michael Hansen, a senior scientist at the US Consumers Union, who disagrees with the FDA's ruling that genetic engineering in itself does not constitute a material difference between the GM fish and its wild counterpart.

The FDA's own scientific evaluation, however, is that the modified genes inserted into the GM salmon are unlikely to give rise to any adverse effects to human health, either directly from toxic effects such as allergic reactions, or indirectly from metabolic by-products of the genetic modification.

In the US, the FDA has already ruled that meat from cloned cattle, pigs and goats is as safe to eat as meat from conventionally bred livestock. GM animals, however, fall under different legal provisions and as such must receive formal approval before they can be sold for human consumption.

If, as expected, the FDA eventually approves the sale of the GM salmon, it will mark an important precedent in the technological changes to the human food chain that some scientists believe are essential if we are to feed the extra three billion people expected to be living on the planet by the middle of the century. Its approval will lead to calls for similar licences in Britain and the rest of Europe.

AquaBounty Technologies argues that biologically the fish are no different to wild salmon, yet can be grown on fish farms more efficiently than conventional farmed salmon, making them less harmful to the environment. Because GM salmon are designed to be reared in tanks on land, they are closer to the markets, thus lowering transport costs and the corresponding carbon footprint.

Scientists have warned that the marine environment, which has already suffered from decades of intensive overfishing, is close to collapse. Yet the demand for fish has increased at a time when stocks have dwindled. Humans face a stark choice between giving up eating many kinds of wild-caught fish, or turning to alternatives such as captive-bred animals. GM technology offers one potential solution to the problem of feeding a growing human population, but it is one solution among many.

What is clear is that an overwhelming proportion of consumers have yet to be convinced of the benefits of GM animals for food.

GM Foods: The facts

Genetically modified (GM) animals are created using a technology which alters their DNA, thus changing their genetic make-up permanently. Often these "transgenic" animals have DNA inserted into their genome from another, unrelated species.

Agricultural researchers have experimented extensively with GM technology to improve the performance of domestic animals. Growth-hormone genes were seen as a way of boosting muscle growth, but many early experiments were stopped after disastrous results.

The most notable failure in this research was the "Beltsville pig" produced by the US Department of Agriculture in the early 1980s. The pig had a human growth-hormone gene inserted into its DNA which was supposed to make it grow faster and leaner. However, this caused disturbing growth deformities that crippled the animals.

Other attempts at creating GM animals have focused on the possibility of producing valuable human proteins in their milk. This "biopharming" was seen as a way of making new drugs that could not be easily made by other means.

Similar research has centred on creating GM animals with organs that could be transplanted into humans without fear of tissue rejection.